* Physical Changes: Involve alterations to a substance's physical properties (shape, size, state of matter) but not its chemical composition.

* Chemical Changes: Result in the formation of new substances with different chemical compositions.

When a lake freezes, the water molecules (H₂O) simply change their arrangement:

* Liquid Water: Water molecules move freely and are relatively far apart.

* Ice: Water molecules become more ordered, forming a crystalline structure where they are closer together.

Key Points:

* No new substances are created: The chemical composition of water (H₂O) remains the same in both liquid and solid states.

* The change is reversible: When the temperature rises, the ice melts back into liquid water.

Therefore, the freezing of a lake is a physical change, not a chemical change.